Bipolar plates of this type are packed closely on top of one another in so-called “stacks” and are arranged in series-connected fuel cells as an intermediate layer between the individual fuel cells. Thus they come to abut against respectively an electrode or gas-diffusion layer of two adjacent fuel cells, against an anode and a cathode. The bipolar plate here fulfils a plurality of functions, namely providing an electrically conductive connection for the series-connected fuel cells, conveying reactants to the electrodes of the adjacent fuel cells, carrying away the reaction products, cooling the fuel cells by heat transfer e.g. to an adjacent cooling chamber, and finally sealing connecting points of the fuel cells in a stack.
In order to accommodate as many fuel cells as possible in the smallest possible space and with the lowest possible total weight of the stack, and thus to achieve a high gravimetric and volumetric power density, an attempt is made to produce bipolar plates having as low a weight as possible and as small a thickness as possible. Using thin foils formed from metals such as e.g. stainless steel, aluminium or titanium for this purpose to manufacture bipolar plates is known. These foils are so shaped, e.g. by embossing, that a channel structure is formed which is suitable for conveying reactants to the electrodes of the adjacent fuel cells and for carrying away reaction products. As a result of the required rigidity of a bipolar plate, however, limits are set to the reduction of the thickness of foils of the prior art used; a minimum thickness of roughly 0.1 mm seems to be necessary. Correspondingly, according to the prior art, limits are also set to the gravimetric and volumetric power densities of fuel cell stacks, which in the case of desirable output voltages still lead to stacks of a disadvantageously high weight and large size.